Chapter 4 -- Decimals

Transcription

1 Chapter 4 -- Decimals $34.99 decimal notation ex. The cost of an object. ex. The balance of your bank account ex The amount owed ex. The tax on a purchase. Just like Whole Numbers Place Value from the decimal point: ones, decimal (and), tenths, hundredths, thousandths, ten-thousandths, hundredthousandths, see page 235 Write in words ex. Write a check for $38.43 ex. You buy two items that sell for $85.90 and $ You pay a total of $13.22 in taxes. How much should you write a check for? Write it. Notice that we can write 8 / 4 = 12/3 = 24/6 = We can write fractions as decimals Sometimes they terminate some times they do not ( nonterminating) ex. 7/10 = 3/8 = but 2/3 = Other fractions: 7/25 = ex. 42/1000 = 7/9 = What place value is the digit 3 in the number ? 51

2 Write as a decimal. 3/10 =, 93/100 = 58 /1000 = Write as a fraction. 0.4 =, 0.24 = = Write in words = = Order. Insert the correct symbol ( < or > ) Rounding: Round the number to the given place value tenths thousandths Addition and Subtraction of decimals We still have the same rule of signs ex. Add: ex. Subtract evaluate: x - y if x = and y = Estimate:

3 Multiplication of Decimals: sum of the decimal places of the factors have to equal the decimal places of the product = = x 2.01 = Special Case: When multiplying by powers of 10 such as 10, 100, 1000: ex. 10 x 3.25 = x 100= x 10 5 = Division: 8 4 = 2 ; 4 is the divisor and 2 is the quotient Move the decimal point in the divisor to the right so that the divisor is a whole number. Move the decimal place in the dividend the same number of places. Place the decimal point directly above. ex = ex Special Case: Division by powers of 10; = = = We can write every fraction as a decimal if we interpret the fraction bar as a division. When we write a fraction as a decimal we get two types of decimal expression; terminating and nonterminating ex. 3/5 = 5/8 = 3/ 11 = ex. 9/1000 = ex. 2 5/9 = 53

4 We can also reverse the process and write a decimal expression as a fraction. ex = ex = ex = ex = Estimate by rounding. ex = ex = ex = Evaluate if x - = 0.1 and y = ; - x 2 = - xy = Compare decimal expressions(and fractions) : ex. 9/ ex. 7/ ex. 8/ Other Examples: ex. Your annual salary last year was $ What was your monthly salary? ex. You travel 34.2 miles per gallon. If you have a car with a 12.8 gallon capacity, then what is the maximum number of miles that you can travel? 54

5 ex. A year consists of 52 weeks. You get a biweekly salary of $850. What is your yearly pay? ex. At the end of each of month you save a fixed amount into a savings account. At the end of 1 ½ years you have $ How much did you save each month? 55

7 Every positive number has two square roots; one positive and one negative. We use the symbol to represent the positive square root. Notation: x is called the radical, x is is called the radicand Each of these numbers has two square roots: 4 and 25 since ( -2) 2 = 4, ( 2) 2 = 4 ; ( -5 ) 2 = ( 5) 2 = 25 The radical only refers to the positive square root. 49 = 7, if we want the negative value we write 49 = 7 More Examples: Find all of the square roots of 64, 121, 400, Find 81 =, 169 =, 144 = What is = = 5 36 = = 9 = 16 57

8 Not all whole numbers are perfect squares what do we do when we try to find the square root of such a whole number? 26 = 53 = What two consecutive whole numbers does 37 lie between? < 37 < We can give approximations with a calculator or an algorithm we also have exact values. Property of radicals ab = a b. We can use this property to simplify radicals - Find (exact value ) 20 = 50 = 18 = 80 = 58

9 Real Numbers Now that we have introduced radicals, we are ready to complete the set that we call the set of real numbers. Sets of Numbers { 1, 2, 3, } { 0, 1, 2, 3, } { -3, -2, - 1, 0, 1, 2, 3, } A rational number is a number that can be written as a fraction a/b, where both a and b are integers Every rational number has a decimal expression that is terminating or repeating. 1/5 = 0.2, 3/8 = 0.375, 5/9 = = = An irrational number is a number whose decimal representation never terminates or repeats -- can not be written as a fraction of integers π = , 2 =, , , The set of rational numbers and the irrational numbers when combined create the set of real numbers We can plot these numbers on a number line --- ex. Plot -5, 7, 3.5, \/ 3 ex. We can also write real numbers on the number line with inequalities a) Write down all of the real numbers less than 2 b) Write down all of the real numbers greater than or equal to 1 c) write down all the numbers between -2 and 3 59

15 These types of rules help us multiply monomials together but what about the product of polynomials? Products of powers of 10. What is ? = Find Quotients of powers of 10. What is ? = Find = Convert to a decimal 9/16 = 7/4 = 5/3 = 3 2/9 = Exponents Just like we worked with natural numbers, whole numbers, integers, we can work with fractions. ex. ( 2/3 ) 2 = ex. ( 2 1/5 ) 2 = ex. ( 2 ½) 3 ( 1 ½ ) 3 = 65

16 HW: page 322 1, 5, 10, 15, 20, 25, 95 Math 130A Week 6 day 2, October 3, Quiz # Homework 20, 15, 10, { 0, 1, 2, 3, } is called the set of 0.3 The set of rational numbers consists of and proper fractions or mixed numbers. Each of these numbers can be written as a fraction and have a terminating decimal expression or have a repeating part if it is nonterminating 1. Write as a fraction Write as a fraction in simplest (reduced) form; Write in decimal form a) 3/1000 = b) 3/8 = 4. Write in words; Round to the nearest thousandth Perform the given operation ( add, subtract, multiply, divide ) a) ( ) = b) = c) = d) = 7. Evaluate. x 2 - y if x = and y =

17 8. Find the solution of each of the following equations. a) 0.2 x = 9.8 b) 4.2-2x = 6.8 More HW problems on page Square roots, radicals \/, Product Property of Square roots Name Math 130A Quiz #12, October 5, Homework 20, 15, 10, 0 1. Give me an example of an improper fraction. 2. Write 6/ 5 in decimal form. 3. Solve for x x = = = = 7. A pen sells for $1.50 after taxes. You pay with $20 and get $6.50 back in change how many pens did you buy if all your money went towards the purchase of pens % of the students in Math 130A are known to drop out of school at the end of the semester. If there are 240 students enrolled during the semester, then how many will return next semessteer? ( HINT: use the fact that 6 % = 0.06 ) 67

18 Name Math 130A October 2, 2002 week 6 day 2 1. What do you call the set of real numbers that can be written as fraction ( have terminating decimal expressions or repeat )? 2. Find the square roots of Simplify the following radicals. a) \/ 49 = b) \/ 100 = c) \/ 1600 = d) \/ 16 \/ 25 = e) 4 \/ 36 = 4. Complete the formula \/ a b = 5. Write the following in simplest form by using the formula in #4. a) \/ 8 = b) \/ 32 = 6. Use a number line to plot x > 4 68

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